C++ QFileSystemMetaData::exists方法代码示例

static inline bool _q_checkEntry(QFileSystemEntry &entry, QFileSystemMetaData &data, bool resolvingEntry)
{
    if (resolvingEntry) {
        if (!QFileSystemEngine::fillMetaData(entry, data, QFileSystemMetaData::ExistsAttribute)
                || !data.exists()) {
            data.clear();
            return false;
        }
    }

    return true;
}

/*!
    \since 5.2

    Returns \c true if the \a file exists; otherwise returns \c false.

    \note If \a file is a symlink that points to a non-existing
    file, false is returned.

    \note Using this function is faster than using
    \c QFileInfo(file).exists() for file system access.
*/
bool QFileInfo::exists(const QString &file)
{
    QFileSystemEntry entry(file);
    QFileSystemMetaData data;
    QAbstractFileEngine *engine =
        QFileSystemEngine::resolveEntryAndCreateLegacyEngine(entry, data);
    // Expensive fallback to non-QFileSystemEngine implementation
    if (engine)
        return QFileInfo(new QFileInfoPrivate(entry, data, engine)).exists();

    QFileSystemEngine::fillMetaData(entry, data, QFileSystemMetaData::ExistsAttribute);
    return data.exists();
}

//static
QFileSystemEntry QFileSystemEngine::canonicalName(const QFileSystemEntry &entry, QFileSystemMetaData &data)
{
    if (entry.isEmpty() || entry.isRoot())
        return entry;

    QFileSystemEntry result = absoluteName(entry);
    if (!data.hasFlags(QFileSystemMetaData::ExistsAttribute))
        fillMetaData(result, data, QFileSystemMetaData::ExistsAttribute);
    if (!data.exists()) {
        // file doesn't exist
        return QFileSystemEntry();
    } else {
        return result;
    }
}

//static
bool QFileSystemEngine::setCurrentPath(const QFileSystemEntry &entry)
{
    QFileSystemMetaData meta;
    QFileSystemEntry absname = absoluteName(entry);
    fillMetaData(absname, meta, QFileSystemMetaData::ExistsAttribute | QFileSystemMetaData::DirectoryType);
    if(!(meta.exists() && meta.isDirectory()))
        return false;

    RFs& fs = qt_s60GetRFs();
    QString abspath = absname.nativeFilePath();
    if(!abspath.endsWith(QLatin1Char('\\')))
        abspath.append(QLatin1Char('\\'));
    TInt r = fs.SetSessionPath(qt_QString2TPtrC(abspath));
    //SetSessionPath succeeds for non existent directory, which is why it's checked above
    if (r == KErrNone) {
        __ASSERT_COMPILE(sizeof(wchar_t) == sizeof(unsigned short));
        //attempt to set open C to the same path
        r = ::wchdir(reinterpret_cast<const wchar_t *>(absname.filePath().utf16()));
        if (r < 0)
            qWarning("failed to sync path to open C");
        return true;
    }
    return false;
}

//static
QFileSystemEntry QFileSystemEngine::canonicalName(const QFileSystemEntry &entry, QFileSystemMetaData &data)
{
    if (entry.isEmpty() || entry.isRoot())
        return entry;

#if !defined(Q_OS_MAC) && !defined(Q_OS_QNX) && !defined(Q_OS_ANDROID) && !defined(Q_OS_HAIKU) && _POSIX_VERSION < 200809L
    // realpath(X,0) is not supported
    Q_UNUSED(data);
    return QFileSystemEntry(slowCanonicalized(absoluteName(entry).filePath()));
#else
    char *ret = 0;
# if defined(Q_OS_DARWIN)
    ret = (char*)malloc(PATH_MAX + 1);
    if (ret && realpath(entry.nativeFilePath().constData(), (char*)ret) == 0) {
        const int savedErrno = errno; // errno is checked below, and free() might change it
        free(ret);
        errno = savedErrno;
        ret = 0;
    }
# elif defined(Q_OS_ANDROID)
    // On some Android versions, realpath() will return a path even if it does not exist
    // To work around this, we check existence in advance.
    if (!data.hasFlags(QFileSystemMetaData::ExistsAttribute))
        fillMetaData(entry, data, QFileSystemMetaData::ExistsAttribute);

    if (!data.exists()) {
        ret = 0;
        errno = ENOENT;
    } else {
        ret = (char*)malloc(PATH_MAX + 1);
        if (realpath(entry.nativeFilePath().constData(), (char*)ret) == 0) {
            const int savedErrno = errno; // errno is checked below, and free() might change it
            free(ret);
            errno = savedErrno;
            ret = 0;
        }
    }

# else
#  if _POSIX_VERSION >= 200801L
    ret = realpath(entry.nativeFilePath().constData(), (char*)0);
#  else
    ret = (char*)malloc(PATH_MAX + 1);
    if (realpath(entry.nativeFilePath().constData(), (char*)ret) == 0) {
        const int savedErrno = errno; // errno is checked below, and free() might change it
        free(ret);
        errno = savedErrno;
        ret = 0;
    }
#  endif
# endif
    if (ret) {
        data.knownFlagsMask |= QFileSystemMetaData::ExistsAttribute;
        data.entryFlags |= QFileSystemMetaData::ExistsAttribute;
        QString canonicalPath = QDir::cleanPath(QString::fromLocal8Bit(ret));
        free(ret);
        return QFileSystemEntry(canonicalPath);
    } else if (errno == ENOENT) { // file doesn't exist
        data.knownFlagsMask |= QFileSystemMetaData::ExistsAttribute;
        data.entryFlags &= ~(QFileSystemMetaData::ExistsAttribute);
        return QFileSystemEntry();
    }
    return entry;
#endif
}